This invention relates generally to the field of pumps, in particular variable displacement pumps utilized in automotive vehicles. These pumps are designed to improve the fuel efficiency of automotive vehicles.
In a power steering system of a vehicle, a variable displacement pump is a hydraulic pump that responds to the needs of the power steering system, as well as to changes in revolutions per minute (RPM) of the engine, by supplying fluid to the power steering system. Variable displacement pumps reduce the input torque requirements on the front-end accessory drive (FEAD) of the driving engine. In this displacement pump, the discharge flow rate increases or decreases in accordance with the speed of the engine. As the shaft speed, which is controlled by a drive belt from an engine of the vehicle, increases, the pump pressure and output flow of the pump also increases. When the pump reaches a desired shaft speed, a spool valve, and a spring allow pressure to be exposed on one side of a cam ring structure in a variable displacement pump. This pressure decreases eccentricity of the cam ring to the pump shaft center by providing a force to swing the cam ring. The decrease in eccentricity decreases the pump displacement by moving the cam ring center point towards the shaft center.
In order to control the flow rate of fluid through the variable displacement pump, various techniques have been developed. One such technique is described in U.S. Pat. No. 5,562,432, which discloses a conventional variable displacement pump having a cam ring that is moved by the pressures of the first and second fluid pressure chambers and the biasing force of the compression coil spring is formed in the second fluid pressure chamber. The movement of the cam ring occurs in accordance with an increase or decrease of the supply flow rate of the fluid accompanying a change in rotational speed of the pump, thereby controlling the pump volume to a required value. However, a problem exists in appropriately controlling the swing motion of the cam ring.
The present invention provides, in one embodiment, a variable displacement pump. A pump body has an outer ring defining an inner cavity, where the inner cavity further defines a pump suction path and a pump discharge path in fluid communication with the inner cavity. A cam ring is pivotably supported in the inner cavity by a pivot pin formed on a portion of an inner diameter of the outer ring. An actuated cam is formed on the cam ring. An actuator is linked through the actuated cam to the cam ring for moving the cam ring in a pivotable motion. A control module is linked to the actuator.
In a further embodiment of the invention a variable displacement pump is provided. A pump body has an outer ring defining an inner cavity, where the inner cavity further defines a pump suction path and a pump discharge path in fluid communication with the inner cavity. A cam ring is pivotably supported in the inner cavity by a pivot pin formed on a portion of an inner diameter of the outer ring. An actuator is linked through a screw arm to the cam ring for moving the cam ring in a pivotable motion. A control module is linked to the actuator.
In another embodiment of the invention a device is provided for adjusting the amount of fluid flowing through a variable displacement pump. A control module is configured to receive measurements of pressure from a power steering system and measurements of an engine speed from an engine of a vehicle, the module is configured to produce pump control signals. A cam ring is disposed in the variable displacement pump, the ring being actuatable in response to the signals from the control module.
In another embodiment of the invention a method for adjusting the amount of fluid flowing in a variable displacement pump is disclosed. The method includes providing a cam ring pivotably supported in an inner cavity of a pump body by a pivot pin formed on a portion of an inner diameter of the pump body and a portion of an outer diameter of the cam ring. An actuator is provided as a link to the cam ring. The control module receives measurements from an engine and measurements from a power steering system of a vehicle. The measurements are transmitted from the control module to the actuator. The cam ring is adjusted via the actuator in response to the measurements.
In yet another embodiment of the invention a system is provided for adjusting the amount of fluid flowing in a variable displacement pump in a vehicle. A power steering system includes a variable displacement pump having a pumping chamber and a pivotably mounted cam ring inside the pumping chamber. An engine is mounted in the vehicle. A control module is configured to receive measurements of pressure from the power steering system and measurements of an engine speed from the engine to move the cam ring and adjust pressure in the variable displacement pump.